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 phychotron
Medicated
Registered: 02/17/11
Posts: 1,995
Loc: Earth (mostly) 
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 Day build #2: A simple power relay 
#825267 - 04/06/17 11:13 PM (7 years, 7 months ago) |
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Have you ever needed to run more electricity through your timer than what it is rated for? Or control multiple power sources from one timer? Do you need to take a load off a circuit?
If you need to power much more equipment than what your timer or source is capable of handling then you will need a power relay.
A relay is real simple. Its a switch that is controlled by electricity instead of a person. That electricity is supplied by your timer when it is on and the LOAD is plugged into another outlet that gets switched on or off.
Supplies are simple and cheap
Heavy duty 3-prong power cord (goodwill, PC power cord 14guage rated for 13A, $2)
Two prong power cord (cheap three outlet extension cord, brand new, $1.50)
2 power outlets ($1.50/both home depot)
2 junction box ($2 Home depot)
2 outlet face plate ($.75)
Relay: 120V DPDT coil (Ebay $2.25 china import, U.S $7-25)
Total around $10
Tools include:
wire cutters, strippers, screwdrivers. The meter helps but not needed if you trust the wiring diagram.
Both power wires get the female end cut off and fed through the junction box. The relay gets wired to the Contact terminals. The ribbed side is neutral (-).
There are two sides to this relay because its a "double pole" and can control 2 circuits. We're only using one side or the other. In this case, the "right" side.
 or 
And the relay is also "double throw" meaning it has two positions. Basically an input with two possible outputs. One output is always connected- which one depends on the Contact being powered.
So I looked at the circuit and figured it out but to be safe I tested it. Using the meter on beep-when-connected mode I verified the output of the LOAD, to determine which was normally open or normally closed.
  
From there it was simple. I wired the green wire to the green screw on both of the outlets. The black wire (hot) was run to one side of one outlet. Then the two outlets were connected with some solid core wire I had for that type of work (negative to negative, positive to positive)
The white wire (neutral) was wired into the input side of the relay. Another wire was run to the opposite side of the other outlet so that each outlet had one power input wire on the outer side.
I used a solid piece for the other side of the relay and it worked well to hold the relay in place, but if you need a little wire to use cut the LOAD power cord down a few inches and use the wire from it to connect the outlet to the relay.
Powered up it lights up inside and you can hear the solenoid click.
Mount the outlets and face plate and done.
 
Total time about 15 minutes.
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Any help given is for educational purposes only. Its your responsibility not to break any applicable laws
 Bamboo Bongs I make | Perfect Dry and Cure | Grapegod under LED
“Human beings, vegetables, or cosmic dust, we all dance to a mysterious tune intoned in the distance by an invisible player.” ~ Albert Einstein
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Data
That Guy
Registered: 08/12/08
Posts: 4,035
Loc: Southwestern US
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Re: Day build #2: A simple power relay [Re: phychotron]
#825268 - 04/07/17 10:22 AM (7 years, 7 months ago) |
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This is a great post. I've been using power relays in some of my automation projects for years now and never thought to post on how to build one.
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“The Universe is under no obligation to make sense to you” -NDT
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phychotron
Medicated
Registered: 02/17/11
Posts: 1,995
Loc: Earth (mostly)
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Re: Day build #2: A simple power relay [Re: Data]
#825269 - 04/07/17 11:37 AM (7 years, 7 months ago) |
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Thanks. I was originally going to use it to control a fan with 2 speed controls, day and night.
It could also be used with a photo sensor instead of the contact wire (Load provides power to sensor & contact.) That way it just senses when the lights are on and will turn the power on. I opted for the corded version cause those photo sensors all go out eventually. For $2 its not that bad but its still something to break.
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Any help given is for educational purposes only. Its your responsibility not to break any applicable laws
Bamboo Bongs I make | Perfect Dry and Cure | Grapegod under LED
“Human beings, vegetables, or cosmic dust, we all dance to a mysterious tune intoned in the distance by an invisible player.” ~ Albert Einstein
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